The growing complexity of semiconductor device designs in advanced technology nodes involves not only a decrease in structural dimensions and higher complexity of the device design, but also the utilization of new materials. Device yield and performance become increasingly sensitive to material properties, such as composition, stress, crystallinity and doping, which in turn require appropriate metrological solutions for process control.
Various optical measurement techniques have been developed for measuring the strain and other properties of a material.
U.S. Pat. No. 7,274,440 describes systems and methods for measuring stress in a specimen. One system includes an optical subsystem configured to measure stress-induced birefringence in patterned structures formed on the specimen. In some embodiments, the optical subsystem may be configured as a spectroscopic ellipsometer, a multi-angle laser ellipsometer, a polarimeter, a polarized reflectometer, or some combination thereof. The system also includes a processor coupled to the optical subsystem. The processor is configured to determine stress in a material of the patterned structures using the stress-induced birefringence measurements. One method includes measuring stress-induced birefringence in patterned structures formed on the specimen using an optical technique. The method also includes determining stress in a material of the patterned structures using the stress-induced birefringence measurements.